Brazing method for carbide tipped saw blades

ABSTRACT

A machine for brazing carbide tips onto the cutting teeth of circular saw blades comprising a vertical saw support jig attached to a cabinet enclosing carbon arc brazing apparatus therein. A first electrode is attached to the saw which is urged in a direction so that a carbide tip disposed against a saw tooth is forced into engagement with a second (carbon) electrode. A clearance gauge assures proper lateral placement of the tip against the saw tooth. The carbon arc brazing apparatus includes a variable rheostat calibrated to show differing saw thicknesses, at indices where the brazing area is brought to desired proper temperature related to the indicated saw thickness. A timer thermostat is used in the brazing circuit to prevent excess heat in the brazing area. The method for brazing a carbide tip to a circular saw tooth edge includes placing the saw in a jig, inserting a carbide tip to be brazed between a carbon electrode and the saw tooth, retaining the tip against the tooth by weight of a brazing electrode attached to the saw outside of the brazing area, brazing by moving a silver solder rod about the junction of the tip and saw tooth, and trimming the brazed, tipped saw tooth to a cutting edge.

United States Patent [191 Stevenson [451 May 22, 1973 [54] BRAZINGMETHOD FOR CARBIDE [57] ABSTRACT TIPPED SAW BLADES A machine for brazingcarbide tips onto the cutting [76] Inventor: Norman A. Stevenson, 1632East teeth of circular saw blades comprising a vertical saw MercedAvenue, West Covina, support jig attached to a cabinet enclosing carbonarc Calif. 91791 brazing apparatus therein. A first electrode isattached [22] Filed: June 7 1971 to the saw which is urged in adirection so that a carbide tip disposed against a saw tooth is forcedinto en- PP No.1 150,626 gagement with a second (carbon) electrode. Aclearance gauge assures proper lateral placement of [52] U.S. Cl...76/l12, 219/77, 76/25 the p against the saw tooth- The carbon arc b g[51] Int Cl. ..B23d 65/00 apparatus includes a variable rheostatcalibrated to [58] Field of Search ..76/ 112; 143/133; show differingsaw thicknesses, at indices where the 219/77; 29/484 brazing area isbrought to desired proper temperature related to the indicated sawthickness. A timer ther- Referencfis Cited mostat is used in the brazingcircuit to prevent excess UNITED STATES PATENTS heat in the brazingarea. The method for brazing a carbide tip to a circular saw tooth edgeincludes plac- 2,714,3l7 1955 Drake 12 ing the saw in a jig, inserting acarbide tip to be brazed 2,826,941 3/1958 KoleSh-m "76/112 between acarbon electrode and the saw tooth, retain- 2,890,323 6/1959 Lee..219/l30 Primary Exa miner-Leonidas Vlachos Attorney-Strauch, Nolan,Neale, Nies & Kurz ing the tip against the tooth by weight of a brazingelectrode attached to the saw outside of the brazing area, brazing bymoving a silver solder rod about the junction of the tip and saw tooth,and trimming the brazed, tipped saw tooth to a cutting edge.

3 Claims, 12 Drawing Figures PATENTEDHHZ-ZIHH SHEET 1 OF 4 INVENTORNORMAN A. STEVENSON %w ATP PAIENIEW $733,934

SHEET 2 0Y4 INVENTORQ g NORMAN A. STEVENSON ATTO PATENIED HAY 2 21975sum 3 [1F 4 FIG. 6

INVENTOR NORMAN A. STEVENSON ATTORNE 5 PATENTEB MAY 2 21973 SHEET t UF 4a ii uILll 2 5 RHEDSTAT D'IAL me" to v2" 'iRANsr-oRMER 50A in 250A STD.250V POWERSJLRCE TIMER THERMOSTAT SAW BLADE INVENT OR FIG ,2 NORMAN ASTEVENSON WWW/f4; ATTORNEYS BRAZING METHOD FOR CARBIDE TIPPED SAW BLADESBACKGROUND OF THE INVENTION 1. FIELD OF THE INVENTION The inventionrelates generally to treating saw blade edges and specifically to meansand method for brazing hard carbide cutting bits or tips onto the teethof circular saw blades.

2. DESCRIPTION OF THE PRIOR ART The art of brazing and welding hard tipsof dissimilar material to relatively softer blade stocks so as to form arelatively inexpensive cutting blade having a strong, durable andefficient cutting surface is presently well developed. Early developmentof the art is evidenced by U.S. Pat. No. 1,919,358, issued to Joseph P.Bern, wherein a central circular blade stock is mounted in a ring moldfor forming an entire rim of relatively hard material which is thenfashioned into a saw tooth edge. However, the blade formed by such aprocess is still too expensive to be commercially feasible.

U.S. Pat. Nos. 1,635,217, issued to Ferdinand H. Kirchman, U.S. Pat.Nos. 3,034,378 and 3,110,952, issued to William T. Anderson, and U.S.Pat. No. 3,295,396 issued to Gerhard G. Kolb all disclose methods ofwelding hard cutting tips to bases of softer dissimilar metals. In theKirchman patent, a variable resistance is provided in the weldingcurrent circuit, to regulate the value thereof depending upon thematerials to be welded together. However, a welding operation, asdistinguished from a brazing operation, has inherent disadvantages.First, power requirements make such an operation expensive. Secondly,the welding operation requires some deformation of the two materialsbeing joined. Thus, while the actual weld spot will be secure, areas inboth materials adjacent the weld spot will be weakened and may fracturewhen the resultant product, a tipped saw, is put to use. Thirdly, theamount of current used must be extremely carefully regulated to assure aclean weld without over-heating the materials to be welded beyond theirdeformation limits.

The proposition that brazing is better than welding in the specific artof applying hardened tips to saw blade teeth has been recognized in U.S.Pat. No. 2,528,226 issued to Vernon H. Hildebrant and U.S. Pat. No.2,714,317 issued to Claud E. Drake. But the disclosures of both patentsare uninforrnative as to a specific means and methodology forsuccessfully carrying out the process of attaching hard tips to sawteeth.

The present invention amplifies the prior art by teaching the use of asaw jig attached to a welding machine which is powered down to a currentlevel which will provide sufficient heat for a brazing operation. Thepower supply includes a variable rheostat calibrated to varying sawthicknesses to provide appropriate heat .without deforming the materialsjoined.

SUMMARY OF THE INVENTION It is the principal object of this invention toprovide apparatus for brazing hard cutting tip inserts onto the teeth ofa circular saw blade including a mounting jig with weight means, whichconveniently can be one of the electrodes, to press the individual toothand hard metal tip against the other electrode for brazing.

It is another object of the invention to provide a brazing apparatus ofthe type described which includes a source of electrical power forbrazing having variable rheostat means therein calibrated so that theindices show varying saw blade thicknesses for setting proper brazingcurrents for different thicknesses.

It is yet another object of the invention to provide a brazing apparatusas hereinbefore set forth wherein the electric power supply includestiming means for preventing over-heating of the brazing area arranged tointerrupt current flow after a predetermined time interval.

It is a further object of the invention to provide a saw blade tipbrazing apparatus having a vertically disposed jig for mounting theblade including a clearance guage for efficiently and expeditiouslyplacing a tip to be joined to a blade tooth in proper lateraldisposition with respect to the tooth prior to brazing.

A still further object of the invention is to provide a method ofattaching carbide tips to the teeth of a circular saw blade comprisingthe steps of vertically mounting the saw in a jig with a tip urgedagainst a tooth by one electrode and retaining the tip thereagainst byweight of the other electrode, brazing by means of a silver solder rodmoved about the junction of the tip and tooth after said tooth and tiphave been brought to brazing temperature from a source of electriccurrent, and thereafter trimming the brazed tip to a cutting edge.

Further novel features and other objects of this invention will becomeapparent from the following detailed description, discussion and theappended claims taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS A preferred structural embodiment of thisinvention is disclosed in the accompanying drawings in which:

FIG. 1 is a perspective view of the brazing apparatus including acircular saw jig attached to cabinetry housing a suitable source ofelectricpower;

FIG. 2 is an elevational view of the apparatus as shown in FIG. 1, anddrawn to an enlarged scale;

FIG. 3 is an end view of the apparatus as depicted in FIG. 2;

FIG. 4 is a plan view of the calibration dial used in the electricalpower apparatus;

FIG. 5 is a plan .view, interiorly of the cabinetry illustrating thereverse side of the calibration dial shown in FIG. 4;

FIG. 6 is an end view of the clearance guage used to position a carbidetip on a saw tooth;

FIG. 7 is a partial top plan view illustrating the brazing step;

FIG. 8 is a partial elevational view showing a tip brazed onto acircular saw tooth;

FIGS. 9 and 10 are partial diagrammatic views illustrating use of theinvention with circular saw blades with teeth having hook angles varyingfrom a negative 15 to a positive 45;

FIG. 11 is a partial elevational view showing positioning of theelectrodes in the jig wherein the weight of one electrode presses a tipand adjacent tooth against the other electrode; and

FIG. 12 is a simplified block diagram setting forth the major electricalcomponents of the electric power sup- DESCRIPTION OF THE PREFERREDEMBODIMENTS (Iabinetry 10 housing a suitable source of electric powerhas a circular saw support jig 12 mounted on a side thereof comprising avertical standard 14 and ajaw member 16, piano hinged to standard 14 at18 for holding a circular saw blade 20 with teeth 22 to be tippedadjacent a primary electrode assembly 24. The return circuit clamp orsecondary electrode 26 is in the form of a spring clamp and is securedas shown in FIGS. 2 and 11 outside of a vertical line drawn through thecenter axis of rotation of saw blade 20 so the weight of the clampedelectrode will urge saw 20 rotationally against primary electrodeassembly 24'. A retaining screw 28 is inserted through an elongate slot30 formed through jaw 16 and the center bore 32 of saw 20, and thenthrough a slot 34, mating slot 30 in vertical standard 14; saw 20 isloosely clamped in jig 12 by screw 28 threaded to bolt 36 behindstandard 14. The interior faces of vertical standard 14 and jaw 16 arelined with felt material spacers 38 to prevent teeth 22 of saw 20 fromjamming within the cooperating halves of jig 12. Saw 20 is only looselyretained by screw 28 and bolt 36 thereby permitting the weight of springclamp electrode 26 to rotationally urge the saw 20 counterclockwise, asillustrated in FIG. 2.

Primary electrode assembly 24 comprises an electrode support 40 with acarbon rod 42 slidably received therein. The assembly 24 may have asuitable handle 44 at one end for gripping by an operator. The lower tipcontacting end 46 may be shaped to conform to the forward face of anindividual carbide tip 48 to be brazed to a tooth 22 of a saw 20. FIG.11 illustrates the holding function of electrode 26, as its weight urgessaw 20 to the left, in the direction of arrow 50. to press a carbide tip48 between electrode end 46 and a tooth 22.

Proper lateral placement of carbide tip 48 is assured by means of asimple clearance guage 52 (FIG. 6) comprising a magnetic base 54, placedon saw 20, an arm 56, and aslidable abutment guage 58 retained in apredetermined position in arm 56 by a set screw 60. Abutment guage 58 isset in a desired position depending on the lateral dimension of saw 20as well as the width of carbide tip 48 in order to center the tip on thetooth. Thereafter as each carbide tip is brazed, clearance guage 52 ismerely moved along the periphery of saw 20 from tooth to tooth and eachcarbide tip 48 is pressed against its associated tooth just prior tobraz- Cabinetry 10 houses a suitable source of electric power, such as astandard, commercially available 250 amp. arc welder power supply 61(FIG. 12). Mounted on cabinet 10 are an on-off switch 62, utilitydrawers 64,64, a louvre 66 which provides an exhaust for the arc weldercooling fan system (not shown) and a variable rheostat 68 (FIGS. 1,2,4,5and 12) which is interposed in the wiring circuit of the standard arewelder power supply. Rheostat 68 is calibrated so its indices showvarying saw blade thicknesses which may be from one-sixteenth toone-half inch as shown in FIG. 4. In conjunction therewith, a timerthermostat 70 (FIG. 12) is also inserted in the control circuit of thestandard are welder power supply, which, once brazing temperature isreached in the vicinity of a carbide tip 48 and tooth 22, will continuecurrent therein for a short period of time (the adjustment range being 0to 30 seconds in the preferred embodiment) whereafter current will beinterrupted to avoid overheating. The individual contacts 72 and leads73 of rheostat 68 are illustrated in FIG. 5.

The operation of the apparatus comprises individually brazing a tip 48to each tooth 22 in station fashion, proceeding from tooth to tooth ofsaw 20 until the entire saw blade is complete. Each individual step ofbrazing is brief and relatively simple. First, a tip 48 is placedbetween electrode end 46 and a tooth 22, whereafter it is properlylaterally disposed by clearance guage 52. Dial pointer 74 of rheostat 68is turned to the proper thickness of saw blade 20. Current is turned onto bring the tip 48 and tooth 22 to brazing temperature, which takes buta few seconds unlike a welding operation where a much longer period oftime is required to bring the area up to a temperature level suitablefor welding. Thereafter, a silver solder rod 76 is moved about thejunction of tip 48 and tooth 22 as shown in FIG. 7. During this step,timer thermostat 70 effectively prevents overheating. Current is turnedoff, whereafter saw 20 is hand indexed to the next tooth 22 to repeatthe process. During indexing, screw 28 need not be adjusted since blade20 is only loosely retained in jig 12, and secondary electrode 26 heldwith its spring clamp is readily shifted up to a new location afterseveral tip brazing operations; its precise location on blade 20 is notcritical. It need only be in a position to place a slight rotationalbiasing force on the saw to urge a tooth 22 and its tip 48 againstprimary electrode 24 in order to retain the carbide tip in place. Thecompleted tooth 22 with a tip 48 brazed thereto is shown in FIG. 8.

The simplicity of the apparatus makes it useful on circular saw bladesof greatly varying thicknesses and radial dimensions, as well as toothhook angles which, conventionally, vary from a negative 15 (FIG. 9) to apositive 45 (FIG. 10) depending on the intended purpose of the saw. Sawtooth 22 may be recessed to receive a tip 48 (FIG. 8) or may be plainedged (FIGS. 9 and 10). Once all of the teeth 22 and tips 48 have beenbrazed, the carbide tips 48 may be ground to a sharp cutting edge inconventional fashion (not illustrated).

The invention may be embodied in other specific forms without departingfrom the spirit or essential characteristics thereof. The presentembodiment is therefore to be considered in all respects as illustrativeand not restrictive, the scope of the invention beingindicated by theappended claims rather than by the foregoing description, and allchanges which come within the meaning and range of equivalency of theclaims are therefore intended to be embraced therein.

What is claimed and desired to be secured by Letters Patentis:

1. A method of brazing a hard tip to a saw tooth of a circular saw bladecomprising the steps of placing the circular saw in a jig, inserting ahard tip between a saw tooth and a brazing electrode, retaining the tipagainst the saw tooth by means secured to the blade to rotationally urgethe tooth with said tip against the brazing electrode, bringing thetooth and tip at least at their cluding the further step of grinding thehard tip to a sharp cutting edge upon completion of the brazing step.

3. The method of saw tooth brazing of claim 1, wherein the steps ofretaining the tip against the saw tooth includes centrally positioningthe hard tip on the saw tooth by preset guage means.

- UNITED sTA'l zcs PA'IICNT 033 mm 'CERTiFICATE OF CGRRECHGN Patent No.3,733,934 Dated May22, 1973 Norman A. Stevenson Invenrofls) It iscertified that error appears in the above identified patentand that saidLetters Patent are hereby corrected as shown below:

7 Column l li jne '60, cancel "epparatu's"? and insert ethod--..

co lumn 1, line 61, after "including" insert -=use of--. 3 e I 3 Celumni1, cancel, lines 65-67.

- Column 2, cancel lines 1-15.

Signed and sealed this 25th day 5r December 1973.

(SEAL) Attest:

EDWARD M.FLETG ER,JR. RENE D. TEGTMEYER Attesting Officer ActingCommissioner of Patents UNITED STATES PATI'INT @FFKC'E CERTIFICATE 0FCORRECTIIGN yeten: No. 3,733,934 We May ZZ, 1973 Inventor-(s) Normannson It is certified that error appears in the above=identified patent"and that said Letters Patent are hareby corrected as shown below:

' Column 1, line '60) cance l Y'apparatu's a'nci insert --a method--. I

Co lumn 1, line 61, after "inluding" insrt ==use of' r.

- Column 1, cance lines 63-67;

Column 2, cancel lines 1-15..

Signed and sealed this 25th day er December 1973.,

(SEAL) Attest:

EDWARD M.FLE TCHEB,JR. RENE D. TEGI'MEYER Attesting Officer ActingGomissionr of Patents

1. A method of brazing a hard tip to a saw tooth of a circular saw bladecomprising the steps of placing the circular saw in a jig, inserting ahard tip between a saw tooth and a brazing electrode, retaining the tipagainst the saw tooth by means secured to the blade to rotationally urgethe tooth with said tip against the brazing electrode, bringing thetooth and tip at least at their junction to a temperature level forbrazing by electrical power means, and brazing the tip to the tooth bymoving a rod of silver solder about the junction of the tip and tooth.2. The method of saw tooth brazing of claim 1, including the furtherstep of grinding the hard tip to a sharp cutting edge upon completion ofthe brazing step.
 3. The method of saw tooth brazing of claim 1, whereinthe steps of retaining the tip against the saw tooth includes centrallypositioning the hard tip on the saw tooth by preset guage means.